The present invention relates to a flexible tube for an endoscope.
A flexible tube for an endoscope is generally formed as follows.
1. Belt-like material made of metal or synthetic resin is wound in a spiral fashion at a predetermined diameter to form a spirally-wound tube.
2. Thus formed spirally-wound tube is covered with a braided wire tube which is formed by braiding thin wires.
3. Further, the braided wire tube is coated, on its outer surface, with a sheath (or a layer) made of synthetic resin.
The flexible tube is disinfected with a strong disinfectant after it is used. Therefore, recently, in order to prevent deterioration of the synthetic resin layer by the disinfectant, a coating layer of chemical resistant agent is formed on the outer surface of the synthetic resin.
The coating layer is formed in accordance with a vacuum evaporation on a smoothly finished circumferential surface of the synthetic resin layer. However, such a coating layer is not so adhesive with respect to the synthetic resin. Therefore, the coating layer is gradually removed during usage, and the synthetic resin layer is exposed to outside. In such a situation, if the flexible tube is repeatedly disinfected with using the strong disinfectant, the synthetic resin will be deteriorated.
It is therefore an object of the present invention to provide an improved flexible tube in which the coating layer is difficult to be removed from the synthetic resin layer, and has an excellent property of resistance against the disinfectant.
For the above object, according to a present invention, there is provided a flexible tube for an endoscope, having an outer tube member, a synthetic resin layer being formed on an outer circumferential surface of the outer tube member, a coating layer being formed on the outer circumferential surface of the synthetic resin layer, the outer circumferential surface of the synthetic resin layer being provided with at least one groove or protrusion.
Optionally and preferably, the at least one groove or the protrusion may be provided over substantially an entire length of the flexible tube.
Further optionally, the at least one groove or protrusion extends substantially parallel with an axis of the outer tube member.
The outer tube member may be formed with a plurality of grooves and/or protrusions.
Further optionally, the at least one groove or protrusion may be formed helically on a circumferential surface of the synthetic resin layer.